Ignore PO/POT files during svn-push

[frankiejarrett]

Translation source files (PO/POT) can sometimes add megabytes to a plugin, depending on the number of strings it has and languages it supports. The only files the plugin actually needs to perform localization are the MO binaries.

I am making some assumptions here:

1. If you are bundle translations into your plugin, then you aren't getting community contributions via GlotPress.
2. If you are using dev-lib you are probably using an external public repo, like GitHub, to accept developer and translation contributions.
3. If you aren't, then you must be providing translations yourself or hiring someone to do it.
4. If you aren't do that...then this doesn't apply to you at all, and you should be using GlotPress.

None of the above scenarios require the source translation files to be in the SVN repo.